The present invention relates to a method of mass spectrometry and a mass spectrometer.
Data Directed Acquisition (“DDA”) modes of operation are known in mass spectrometry. In such a mode, mass spectral data of parent or precursor ions is initially acquired in a MS mode. The mass spectral data is then processed to determine candidate parent or precursor ions of interest, from which it is subsequently desired to obtain MS/MS data from. Each candidate parent or precursor ion is then sequentially selected and MS/MS analysis is performed on each candidate parent or precursor ion of interest in turn.
The criteria for switching to MS/MS analysis can be quite complicated and may involve include and exclude lists, adducts and losses etc, i.e. “chemical intelligence”. With recent increases in performance of chromatography separation, ever greater demands are being placed upon the mass spectrometer. In particular, it is desired to increase the number of MS/MS switches whilst maintaining as high a duty cycle as possible.
The desire to increase the performance or duty cycle of mass spectrometers performing Data Directed Analysis (“DDA”) places increased requirements on the mass spectrometer in terms of the time taken to process the initial survey spectrum. However, increasing the time spent processing survey spectra of parent or precursor ions increases the “dead time” of the instrument, i.e. the time when the instrument is not collecting data.
It is therefore desired to provide an improved mass spectrometer and method of mass spectrometry.